Makes me wonder what Newport's lot get up to...
I've glanced into a few mess rooms from passing them with open doors on platforms before now, here are some of them I've seen:
Swansea
Very basic small room. Noticeboard for notices and stuff. Windows for seeing out onto platforms 2 and 3. Couldn't see much else.
Cardiff Central, platforms 3 and 4 (there's another I believe on platform 4)
Again, small room. No windows, the door is usually open as a result. Noticeboards, PC, a few office-related things for it, chairs, desks, think that's about it. I managed to actually enter this one once due to (unintentionally I hasten to add) leaving my holdall with clothes and frozen stews on the 158 I had travelled down in from Hereford. Wearing my NUFC shirt got the usual 'Ah, why'd you wanna support them?' type comments, but it was all normal team fun.
Newport
As per usual, small-ish room, noticeboards, chairs and desks, couldn't see much else.
Rhymney
Standard desks and chairs, noticeboards, I believe there was a PC there, not sure now. Didn't look bad for a rural line's mess-room.
Carmarthen
Same as Newport, didn't see much else but what I saw there.
Hereford
Bigger than most of them, had tea and coffee-making facilities, PC with TRUST on it, notices, a fair few windows. Again, I've been in this one for enquiring about lost property (10-year old tripod, barely used, left on a CT 170 to Nottingham from Cardiff, it then having headed back to Hereford), once or twice for service information or TOC contact numbers. I'd say this one would be my favourite out of the ones I've seen.
Can't remember seeing any others. They're all ATW ones for the reason that I live in this area.